The movement of organelles along microtubules is driven by molecular motors, including members of the cytoplasmic dynein and kinesin superfamilies. The process also requires adaptors which attach the organelles to the motor proteins and regulatory molecules to control the whole process. The identity of the adaptors and regulators are largely unknown. A Drosophila gene, klarsicht, has been shown to be required for two organellar movements that occur at specific times during Drosophila embryogenesis, lipid-droplet migration during gastrulation and nuclear migration during photoreceptor differentiation. KLAR is believed to function in coordinating the attachment of multiple motors to their cargo. My goal is to identify other proteins which function closely with KLAR during nuclear migration in the eye. Using mutagenesis screens, I have identified one locus, egk1, which is particularly interesting because it is a strong enhancer of a dominant phenotype generated by overexpressing klar in the eye. In addition, the egk1 is required for nuclear migration in the developing eye. I propose to clone the egk1 locus and characterize the egk1 mutant phenotype in detail. I will also develop and test hypotheses concerning egk1 function. We believe that egk1 is the second molecule which is involved in attaching specific cargos to motor proteins at specific times during development. The identification of egk1 marks the beginning of our ability to determine the mechanisms by which nuclear migration is coordinated with cell determination during eye development.